天山山区近40年秋季气候变化特征与南、北疆比较

利用新疆1959~1998年的秋季温度降水资料,分析天山山区近40年来秋季气候变化的基本特征,所得结果如下: (1) 天山山区秋季温度在冷暖变化阶段上与北疆的相似性强于南疆,但其秋季降水在干湿变化阶段上与南、北疆不同。 (2) 秋季温度空间分布的同步变化性以北疆为最好,南疆最差,天山山区居中。秋季降水空间分布的同步变化性以南疆最好,天山山区最差,北疆居中。 (3) 20世纪60~90年代,天山山区表现为波动升温,而南疆和北疆表现为持续增温,均以90年代温度最高,80年代是三大区域秋季降水最多的年代。60,70及90年代,三大区域的秋季降水均低于30年均值。     

Contact aureoles as constraints on regional P-T trajectories: an example from the Northern Alabama Piedmont, USA

Abstract Contact aureoles of plutons emplaced into regionally metamorphosed terranes can provide indicators of physical conditions along a portion of regional metamorphic P-T trajectories, thereby allowing reconstruction of more complete P-T loops than would be otherwise possible. In the Northern Alabama Piedmont of the southern Appalachians, Wedowee Group metapelites preserve evidence for two regional metamorphic phases overprinted by contact metamorphism adjacent to the Blakes Ferry Trondhjemite. Textural evidence indicates that an early bt+st+grt assemblage was replaced by bt+chl+grt during the latter stages of regional metamorphism. Changes in AKFM topology, complex Fe-Mg-Ca garnet zoning, and the latestage appearance of epidote indicate that a sequence of continuous reactions (bt+st = grt+ ms followed by chl+ms+Ca-grt+Ca-pl=bt+ (Fe+Mg)-grt+ep) occurred in response to increasing pressure and resulted in the observed changes in mineral assemblage. Pl-ms-bt-grt thermobarometry indicates conditions of 580° 65°C, 8.5±0.8 kbar for equilibration of grt+ bt+chl. Pluton emplacement, subsequent to penetrative deformation, caused textural annealing and mineral re-equilibration by the continuous reaction bt+(Fe+Mg)-grt+ep = chl+ms+Ca-grt+Ca-pl within 50 m of the pluton. Conditions of 510±65°C, 5-7 kbar are inferred. A reconstructed P-T trajectory for this area is characterized by (1) early moderate- T , moderate- P metamorphism; (2) an increase in P to approximately 8.5 kbar; and (3) decompression and slight cooling prior to pluton emplacement. The compressional phase of this path is interpreted to result from underthrusting of the Wedowee metasediments to mid-crustal levels during Palaeozoic crustal thickening. Late-stage decompression prior to intrusion records uplift of these rocks in response to movement on structurally lower thrusts.     

Crustal structure of seismic velocity in southern Tibet and east-westward escape of the crustal material--An example by wide-angle seismic profile from Peigu Tso to Pumoyong Tso

The reflecting events from Moho and other interfaces within the crust are recognized from the wavefield characteristics of P- and S-wave for the 480km long wide-angle seismic profile between Peigu Tso and Pumoyong Tso. Then, seismic crustal structures of P- and S-wave velocities and Poisson ratio under the nearly east-west profile in southern Tibet are interpreted by fitting the observed traveltimes with the calculated ones by forward modelling. Our interpreting results demonstrate that the crustal thickness varies remarkably in the east-west direction, showing a pattern that the crust could be divided into three parts bounded by the west of Dingri and the east of Dinggyê, respectively, where the depth of Moho is about 71km for the western part, about 76km for the middle and about 74km for the eastern. There is one lower velocity layer (LVL) at the bottom of the upper crust with depth of 20-30 km. One of the distinct features is that the thickness of LVL abruptly thins from 24km on the west to 6km on the east. The other is that the velocity variation in the crust along east-west direction for both P- and S-wave displays a feature as quasi-periodic variation. The lower velocity (compared to the average value for the continent of the globe) in the lower crust and three sets of north-southward active normal faults are probably attributed to the coupling process of material delamination in the lower crust, crustal thicking and east-westward escape of the crustal material accompanied with the continental collision between India and Eurasia Plate.     

Validation of an operational forecasting system of sea dike risk in the southern Zhejiang Province,South China

In this study,an operational forecasting system of sea dike risk in the southern Zhejiang Province,South China was developed based on a coupled storm-surge and wave model.This forecasting system is important because of the high cost of storm-surge damage and the need for rapid emergency planning.A comparison with astronomical tides in 2016 and the validation of storm surges and high water marks of 20 typhoons verified that the forecast system has a good simulation ability.The system can forecast relatively realistic water levels and wave heights as shown under the parametric atmospheric forces simulated in a case study;the sea dikes in credible high risk were mainly located in the estuaries,rivers,and around the islands in the southern Zhejiang.Therefore,the forecast system is applicable in the southern Zhejiang with a support to the effective prevention from typhoon storm-surge damage.     

Geology and geochemistry of Jurassic pelagic sediments, Scisti silicei Formation, southern Apennines, Italy

A better understanding of genesis and palaeoenvironmental setting of the Scisti silicei Formation (Lagonegro units, southern Italy) was achieved by means of geochemical analysis integrated with new stratigraphic information. Data show that major and trace element geochemistry of ancient clay-rich beds and banded cherts add new insights into the Mesozoic evolution of the Lagonegro basin. Sedimentary contributions to Jurassic shales sampled during this study were mainly derived from two major sources: (i) a dominant terrigenous fine-grained component, having affinity with average upper continental crust that had not undergone intense weathering and (ii) biogenic siliceous material. The latter component occurs in clay-rich layers from the “basal member” of the Scisti silicei Formation.

Composition varies up section and accounts for changes in the detrital supply due to bathymetric oscillations. The compositional variations from the basal to the overlying member are consistent with a distal source passing in time to a more “proximal” source, as indicated by sharp changes in the concentrations of detrital elements (Ti, Zr and Nb). It is likely that increased detrital input occurred through turbidity current deposition. Finally, the chemical features of the clay-rich layers from the upper cherty portion of the studied succession imply a progressive deepening of the basin.

The lack of any mafic and hydrothermal contributions in the Jurassic shales as well as the continental nature of detrital input suggests that the Lagonegro basin was located between two carbonate platforms, in accordance with the classical restoration of the African–Apulian palaeomargin. Thus, the basin acted as a preferential sink connected to the African cratonic areas through a southern entry point.     

南方地区建筑外墙防渗设计

根据对建筑外墙渗漏原因的分析,从设计角度提出了针对女儿墙、门窗洞口、悬挑构件根部、变形缝、框架梁与填充墙结合部、散水等易渗部位的应对策略。     

Determining the drivers of long‐term aridity variability: a southern African case study

This paper highlights the importance of differentiating between precipitation amount and moisture availability (‘humidity’/‘aridity’) when considering proxy records of climate change. While the terms are sometimes used interchangeably, moisture availability is determined by both (i) precipitation amount and (ii) temperature, through its influence on potential evapotranspiration. As many palaeoenvironmental proxies reflect changes in this water balance rather than purely precipitation amount, it is important to distinguish between the potential relative influences of precipitation and temperature if those records are to be interpreted in terms of climate mechanisms and/or compared with model outputs. As a case study, we explore how precipitation and temperature have determined moisture availability in South Africa's summer rainfall zone over the last 45 000 years. Using quantitative reconstructions of mean annual temperature, summer rainfall amount and an aridity index, our analysis reveals strong spatiotemporal variability in the relative influences of precipitation and temperature on aridity. Temperature is shown to have exerted a considerable and even dominant influence on moisture availability, resulting in elevated humidity during the last glacial period, despite significant reductions in precipitation amount.     

福建地壳运动与地震关系初探

利用福建地震台网88个地震台站于2015年记录的10个月的连续波形数据,基于台网约束下的长短窗特征触发式震相检测的模板事件识别方法和匹配滤波自动检测方法,识别出模板事件919个,匹配滤波后重新识别和定位了共计2 243个地震事件,其中M_L1.0以上地震1 991次,主要集中在M_L1.0—1.5之间,这极大扩充了该震级范围内的福建地震台网目录。重新定位的地震震源深度分布在0—20 km之间,多数发生在10 km内的上地壳。沿长乐—诏安断裂带和永安—晋江断裂带,地震分布集中且表现出明显的分段活动性。在长乐—诏安断裂带上检测到较福建台网目录更多的地震,且地震活动性表现为西南段较强、东北段较弱,沿断裂带的震源深度分布由南向北逐渐变浅,与莫霍面深度的变化相一致;在与之共轭的永安—晋江断裂带上则北西段地震活动更为集中,而东南段地震活动稍显分散。重新识别与精定位后的地震与福建地区地壳水平形变南强北弱、东强西弱的特点相一致。     

Formation of the Jurassic Changboshan‐Xieniqishan highly fractionated I‐type granites,northeastern China: implication for the partial melting of juvenile crust induced by asthenospheric mantle upwelling

Zircon U–Pb ages, major and trace elements, and Sr, Nd and Hf isotope compositions of the Changboshan‐Xieniqishan (CX) intrusion from the Great Xing'an Range (GXAR), northeastern China, were studied to investigate its derivation, evolution and geodynamic significance. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) zircon U–Pb dating yields an emplacement age of 161 ± 2 Ma for the CX intrusion. Bulk‐rock analyses show that this intrusion is characterized by high SiO₂, Na₂O and K₂O, but low MgO, CaO and P₂O₅. They are enriched in large‐ion lithophile elements and light rare earth elements, with marked Eu anomalies (mostly from 0.36 to 0.65), and depleted in heavy rare earth elements and high field strength elements. Most samples have relatively low (⁸⁷Sr/⁸⁶Sr)_i values (0.70423–0.70457), with ε_Nd(t) fluctuating between −0.4 and 2.3. The ε_Hf(t) for zircons varies from 5.4 to 8.7. Sr–Nd isotope modelling results, in combination with young Nd and Hf model ages (760–986 and 549–728 Ma, respectively) and the presence of relict zircons, indicate that the CX intrusion may originate from the partial melting of juvenile crust, with minor contamination of recycled crustal components, and then underwent extensive fractional crystallization of K‐feldspar, plagioclase, biotite, sphene, apatite, zircon and allanite. Considering the widespread presence of granitoids with coeval volcanic rocks, we contend that the CX intrusion formed in an extensional environment related to the upwelling of asthenospheric mantle induced by the subduction of the Palaeo‐Pacific plate, rather than a lithospheric delamination model. Copyright © 2013 John Wiley & Sons, Ltd.